Truck loses power and smokes

[Cougar281]

I just got done working on MBC230's truck and set up a simple tune with the usual turbo vane changes - opened up the vanes at idle and closed at 0mm for the turbobrake. Everything was good for a bit, then while we were going to pick up some supplies, it suddenly lost power and was smoking like crazy, then the power came back and it was fine for the rest of the trip out. I was not able to get any data as I was not watching any data at the time, so on the way back I was monitoring boost levels (that's all I had programmed in my V2 that was useful), and when it did it again, boost level was barely over ambient.

It also smokes a bit off the line and when you get on it, which surprised me as aside from the turbo changes (which are identical to what I've been running in my truck for several years), it is bone stock.

My suspicion is that since the truck has 193,000 stock miles, the turbo vane changes are sending the vanes into positions that they never really hit, so there may be some soot buildup that's making them stick. I have a PSL set up in my V2 now so next time it happens, I can see desired vane position, actual vane position, desired boost & actual boost, so I could confirm, but until I can confirm it, does anyone have any thoughts as to any other possible causes?

 

[mbc230]

Following........

 

[CDR]

sounds like your on to something with turbo vanes sticking. How close in the boost to the target?

 

[mbc230]

John from the Duramax Store

I spoke to John from the Duramax Store and he stated to me he bets it has something to do with the Mass Air Flow values in the tune that was put in. Since it was not happening before the exhaust was installed and now that it is occurring after the exhaust was installed. John was certain it was the mass air flow values. John has stated the turbo on these trucks is rock solid. What do you think Cougar281?

 

[Cougar281]

I spoke to John from the Duramax Store and he stated to me he bets it has something to do with the Mass Air Flow values in the tune that was put in. Since it was not happening before the exhaust was installed and now that it is occurring after the exhaust was installed. John was certain it was the mass air flow values. John has stated the turbo on these trucks is rock solid. What do you think Cougar281?

The tune that was put in was a direct read of your ECM, with only the handful of tables changed. MAF tables were not touched. The fact that it's not constant would likely invalidate the MAF table argument. Most likely, if hte MAF tables were whacked, it would either always be happening, or would always happen under the exact same conditions and would be reproducible at will.

Since I wasn't prepared to log this problem, I don't know where boost was related to the target, but it was barely over ambient pressure, when it should have been much higher. I now have a PSL set up to log Desired vane position, actual vane position, target boost, actual boost, so next time it does it while I'm logging, it should shed some light on it.

One thing I can say with regards to the vane position... I was playing with it for a few minutes last night, and noticed that when I brought it up off idle to cause the vanes to close, then back down to idle, it would drop to 0%, then over a second or three work it's way up to near the target, however, it would generally overshoot the target value and hunt around a bit. I then looked at my truck. It behaved more or less the same, except rather than overshooting the target position, it nailed it and stayed there.

 

[mbc230]

The tune that was put in was a direct read of your ECM, with only the handful of tables changed. MAF tables were not touched. The fact that it's not constant would likely invalidate the MAF table argument. Most likely, if hte MAF tables were whacked, it would either always be happening, or would always happen under the exact same conditions and would be reproducible at will.

Since I wasn't prepared to log this problem, I don't know where boost was related to the target, but it was barely over ambient pressure, when it should have been much higher. I now have a PSL set up to log Desired vane position, actual vane position, target boost, actual boost, so next time it does it while I'm logging, it should shed some light on it.

One thing I can say with regards to the vane position... I was playing with it for a few minutes last night, and noticed that when I brought it up off idle to cause the vanes to close, then back down to idle, it would drop to 0%, then over a second or three work it's way up to near the target, however, it would generally overshoot the target value and hunt around a bit. I then looked at my truck. It behaved more or less the same, except rather than overshooting the target position, it nailed it and stayed there.

I am a newbie you know that.....I just do not get why it was working before then all the sudden it does it after we tuned it and put the exhaust on. I guess you can call me "Murphy" after Murphy's law. Do you think it could work itself out if we drive it enough?

 

[mbc230]

Check this out!

This might be something.......

http://www.dieselplace.com/forum/63...max-black-smoke-acceleration-above-35mph.html

 

[Cougar281]

This might be something.......

http://www.dieselplace.com/forum/63...max-black-smoke-acceleration-above-35mph.html

That's a possibility. The bottom line is the truck isn't getting the boost it needs, which is causing the loss of power and smoking. Once I get a log of it happening, We should have a good idea what it is. If the desired and actual turbo vane positions correlate and there is no boost, then the EGR is really the only place the boost could be going.